Atlantic mackerel is the small fish with the mild flavor and big, meaty texture of a large fish. But there are many other reasons to give it a try. Unlike large apex predators like tuna and swordfish, these mackerel are small, schooling fish that occur in great abundance, providing a truly sustainable harvest. They're caught by hook and line, with little to no bycatch, by traditional fishing families in northern Spain. Since Atlantic mackerel are low on the ocean food chain, they don't have high levels of mercury and other toxins that can concentrate on larger fish. And they are an excellent source of protein, vitamin B-12, and other essential nutrients, with 500 mg of Omega 3 fatty acids per serving.